Border Gateway Protocol Ipv4 (Bgpv4); Autonomous Systems (As) - Dell Z9500 Configuration Manual

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Table of Contents

Border Gateway Protocol IPv4 (BGPv4)

This chapter provides a general description of BGPv4 as it is supported in the Dell Networking Operating System (OS).

BGP protocol standards are listed in the

BGP is an external gateway protocol that transmits interdomain routing information within and between autonomous systems

(AS). The primary function of the BGP is to exchange network reachability information with other BGP systems. BGP generally

operates with an internal gateway protocol (IGP) such as open shortest path first (OSPF) or router information protocol (RIP),

allowing you to communicate to external ASs smoothly. BGP adds reliability to network connections by having multiple paths

from one router to another.

Sessions and Peers

Route Reflectors

BGP Attributes

Multiprotocol BGP

Implement BGP with Dell Networking OS

Configuration Information

BGP Configuration

Enabling MBGP Configurations

BGP Regular Expression Optimization

Debugging BGP

Sample Configurations

Autonomous Systems (AS)

BGP autonomous systems (ASs) are a collection of nodes under common administration with common network routing

Each AS has a number, which an internet authority already assigns. You do not assign the BGP number.

AS numbers (ASNs) are important because the ASN uniquely identifies each network on the internet. The Internet Assigned

Numbers Authority (IANA) has reserved AS numbers 64512 through 65534 to be used for private purposes. IANA reserves ASNs

0 and 65535 and must not be used in a live environment.

You can group autonomous systems into three categories (multihomed, stub, and transit), defined by their connections and

multihomed AS — is one that maintains connections to more than one other AS. This group allows the AS to remain

connected to the Internet in the event of a complete failure of one of their connections. However, this type of AS does not

allow traffic from one AS to pass through on its way to another AS. A simple example of this group is seen in the following

illustration.

stub AS — is one that is connected to only one other AS.

transit AS — is one that provides connections through itself to separate networks. For example, in the following illustration,

Router 1 can use Router 2 (the transit AS) to connect to Router 4. Internet service providers (ISPs) are always transit ASs,

Standards Compliance

Border Gateway Protocol IPv4 (BGPv4)